A knowledge of the means by which forces are transmitted across the articulating surfaces of human joints is important to an understanding of how such joints function. The objective of the proposed project is to gain an in depth understanding of the mechanics and function of the human ankle joint. To gain such insight a loading apparatus and staining technique will be utilized to obtain the contact areas which occur in this joint for loads and positions typical of the walking cycle. From this information estimates of the average contact pressures will be obtained and compared to the force to contact area ratios obtained for the hip and knee joint. To study the mechanics of load transmission a simple model of the ankle joint will be formulated based on observations of joint geometry, cartilage thickness measurements, and the contact patterns. Possible pressure distributions which might act across the contact areas will be obtained from analysis and supported by load deflection experiments performed on the articulated ankle joint. The hypothesis of a uniform pressure distribution at large loads that has been suggested for the human hip will be investigated as regards its applicability to the ankle. A comparison will be made between the contact areas and sites of degenerative change observed in this joint and these findings correlated with similar comparisons made for the hip joint. The role that mechanical factors might play in the initiation and progression of disease processes will be assessed.